The Search for Life Outside the Solar System
The search for life on other worlds is an interdisciplinary endeavour. Understanding the emergence of life on Earth and the evolution of complexity is an essential first step in searching for life elsewhere. New tools must be developed for planets around other stars to be identified and studied in detail. Some of the ways that astronomers are able to observe the Cosmos in the search for life outside the Solar System are shown in the image below.
Life on Earth and its evolution from prebiotic chemistry, sythetic biology, and paleogenetics
By understanding more about the origins of life on Earth, scientists can better understand how life might emerge elsewhere. Although life on Earth gives only one example to study, the knowledge gained here about biology and chemistry can be applied to other environments, to other planets, and can be used to predict whether (and how) life might emerge elsewhere. This is the subject of The Origin of Life.
Earth's evolution and its role in the evolution of Life
Life on Earth today is the product of a more humble beginning. Humans have evolved from prebiotic chemistry to a single cell to our present form over billions of years, a process which was influenced heavily by the evolution of our planet itself and the character of physical law. It is very likely that the form of life we see on Earth is simply not possible in other environments, and that on other planets the evolution of life would follow a much different path. Could life on other planets be conscious? Could it be intelligent? These are the questions of The Evolution of Complexity and The Emergence of Consciousness.
The Identification and Classification of Planets
The search for life elsewhere is less concerned about what life is, but rather what life does. By understanding which chemical byproducts are unique to life, scientists can hope to indentify planets in other solar systems that might contain life by analyzing the chemistry of their atmospheres. Many of the techniques that are used to search for (and analyze) planets elsewhere have evolved from techniques used earlier to study the planets in our own Solar System. More recent techniques have been developed specifically for the purpose of hunting exoplanets. The search for life on other planets is discussed in greater detail in Discovering Exoplanets and Characterizing Exoplanets.